With recent advances in technology, electronic products have been developed to meet the diverse needs in everyday life. As these products are made of various electronic components with different power supply and voltage requirements, the AC power supply from wall needs to be converted to appropriate voltages for each of the electronic components to ensure proper operation.
Conventional AC/DC Converters implement an isolated voltage divider design. After coupling the AC power with rectifiers, a transformer is used to convert the high voltage AC power to low voltage DC power that can be used by the devices. As shown in FIG. 1, the conventional power converter includes a transformer 10, which includes a primary side connected to an electronic switch 12 and a secondary side connected to a load 14, an output capacitor 15 and a voltage divider 16 connected to a processor 18. Through a photo-coupler 20, the processor 18 is connected to a controller 22 that is connected to electronic switch 12 to control its switching state. When a voltage is applied across load 14, the voltage divider 16 retrieves a feedback voltage from the load and sends it to the processor 18 that generates an analog signal accordingly and then transmits it from the secondary side through the photo-coupler 20 to the controller 22 in the primary side. Controller 22 changes the ON/OFF state of electronic switch 12 according to this analog signal. Since the processor 18 comprises of TL431 (three-terminal programmable shunt regulator) and VM (voltage-mode) compensation circuit, it uses zero/pole compensation to compensate the loop gain and bandwidth to reduce the ripple signal of the load voltage, stabilizing the whole system. However, the controller 22 is located on the primary side and thus cannot detect the load voltage directly. There is also delay in TL431 and the VM compensation circuit transmitting the signal generated from the feedback voltage of the load to the controller 22, resulting in the load voltage not being stabilized quickly. Furthermore, it is difficult to be controlled in a continuous current mode (CCM) when having a synchronous rectifier in the secondary side.